Well I don't know what you did but this is what you were supposed to do:
If you want to test your work before investigating that problem. Take off the center dimmer wire you have now and attach a 12 ga jumper from that center dimmer terminal to the battery positive post and try the headlights and the dimmer.
You see here is the deal. YOU said "Jumper wire to both terminals proves that wiring is correct."
I have no idea what terminals. I have no idea what the "proof" is. Something lit up when you did something?
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
